CHICAGO (Reuters) - Brain scans of people in chronic pain
show a state of constant activity in areas that should be at
rest, U.S. researchers said on Tuesday, a finding that could
help explain why pain patients have higher rates of depression,
anxiety and other disorders.

They said chronic pain seems to alter the way people
process information that is unrelated to pain.

"It seems that enduring pain for a long time affects brain
function in response to even minimally demanding attention
tasks completely unrelated to pain," the researchers wrote in
the Journal of Neuroscience.

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Dante Chialvo, a researcher at Northwestern University in
Chicago who worked on the study, said: "People with chronic
pain -- meaning pain that lasts more than six months after
their injury -- have many other issues that affect their
quality of life as much as pain. It is not known where they
come from."

Recent studies have shown that in healthy people, certain
regions of the brain take over during a resting state,
something known as a default mode network. "It takes care of
your brain when your brain is at rest," Chialvo said in a
telephone interview.

When a person performs a task, this network quiets down, he
said, but not in people with chronic pain.

Instead, a front region of the cortex mostly associated
with emotion is constantly active, disrupting the normal
equilibrium.

To study this activity, Chialvo did a type of brain scan
known as functional magnetic resonance imaging on 15 people
with chronic back pain and 15 healthy people.

They gave their volunteers a simple attention task --
tracking a moving bar on a computer screen -- to observe the
brain shifting out of default mode to handle the task.

Both groups performed the task well but when they measured
areas of the brain activated, differences emerged.

"Where we were surprised is the difference in how much
brain they used to do the task compared with the healthy group.
It was 50 times larger," Chialvo said.

They said disruptions in this default network could explain
why pain patients have problems with attention, sleep
disturbances and even depression.

"These findings suggest that the brain of a chronic pain
patient is not simply a healthy brain processing pain
information but rather it is altered by the persistent pain in
a manner reminiscent of other neurological conditions
associated with cognitive impairments," they wrote.